Internal combustion engine



Nov. 28, 1933. F. T. IRGENS INTERNAL COMBUSTION ENGINE 3 Sheets-Sheet 1Filed March 17, 1950 61cm neg a Nov. 28, 1933.

Filed March 17, 1950 3 Sheets-Sheet 2 4 FIG. /6J A6- 0 za I 7 m z/ 52 045 jl 7 i /0 A5- Nov. 28, 1933. F IRGEN 1,936,841

INTERNAL COMBUSTION ENGINE Filed March 17, 1950 v a Sheets-*Shet s 5 v II I 43 3mm /5' Z/ M M I Patented Nov. 28, 1933 UNITED STATES PATENTOFFICE Outboard Motors Corporation, Wis., a corporation of MichiganMilwaukee,

Application March 17, 1930. Serial No. 436,287

34 Claims. (Cl. 123-56) This invention relates to improvements ininternal combustion engines and has particular reference to a novel andimproved rotary valve mechanism which controls the flow of mixture tothe crank case of a two-cycle engine, and also in efiect varies thevolumetric capacity of the crank case at different points of the cycle.

It is the primary object of the invention to improve the volumetricefliciency of two-cycle engines while avoiding difficulties heretoforeexperienced in the way of imperfect mixtures which have resulted fromprevious attempts to increase crank case compression.

It has become standardv practice in two-cycle engine construction tolimit the crank case capacity as much as possible by filling the crankcase almost completely with the cranks and associated parts. By thismeans volumetric efficiency has been improved due to the increased crankcase compression, but there has been .a corresponding decrease in theefficiency of combustion resulting from the high velocity at which thecompressed gases have been transferred to the combustion chamber, whichthey must necessarily enter before the burning charge has beencompletely scavenged.

' In the practice of the present invention I not only use a rotary valvefor the purpose of prolonging and more adequately controllingcommunication between the crank case and the carburetor, but I furtheraccomplish a very important result in designing my rotary valve toprovide an expansion chamber which is made to communicate with the crankcase and transfer port prior to and during transfer of gases from thecrank case to the commistion chamber. 'The additional capacity thusprovided receives a portion of the highly compressed gases in thesub-piston space, and not only maintains such gases more immediatelyadjacent the point of delivery to the cylinder, but also reduces thesub-piston compression to an extent such that the flow of gases to thecylinder is slower and more uniform, thereby promoting better andcleaner scavenging with fewer eddy currents and a much better and morehighly combustible mixture remaining in the combustion chamber. While Ihave referred to crank case compression, it will be observed that thereis very little compression space in the crank case, and that actuallycompression occurs quite largely in the lower ends of the respectivecylinders beneath the pistons operating therein. To avoid loss ofpressure which would be occasioned by transferring gases between therespective cylinders, I prefer to provide each cylinder with its ownseparate carburetion and valve.

Another object of the invention relates to the provision of meanswhereby the rotary valve is permitted to operate at substantiallyuniform rates of rotation notwithstanding periodic or cyclic variationsin rate of rotation of the crank shaft and associated parts.

In the drawings:

Figure 1 is a plan view of a two-cycle twocylinder opposed engineembodying this invention, one of the cylinders and associated valvemechanism being shown in axial section.

Figure 2 is a vertical axial section tothe engine shown in Fig. 1. 0

Figure 3 is a rear elevation thereof.

Figure 4 is a fragmentary detail similar to a portion of Fig. 1, showingthe piston at the end of its compression stroke.

Figure 5 is a view taken in section in the plane indicated at 5-5 inFig. 4.

Figure 6 is a view taken in section in the'plane indicated .at 66 inFig. 4.

Figure '7. is a detail view taken in section in the plane indicated at77 in Fig. 2.

Like parts are identified by the same reference characters throughoutthe several views.

The invention has been shown, byway of illustration, applied to atwo-cycle, two-cylinder opposed engine of an outboard motor, butobviously it may be employed in connection with two-cycle engines havinga different number of cylinders and organized for different purposes.

In this exemplification of the invention a sleeve or so-called shafthousing member 10 supports the crank case 11 upon which are mounted therespective cylinders 12. In the top and bottom of the crank case 11 arebearings for the crank shaft 15, at the upper end of which is the usualfly wheel 16. It will be noted that the crank disks 18, pins 19,connecting rods 20, and connecting rod bearings 21 are so designed as toleave a very small amount of gas' capacity in the crank case, the objectbeing to-fill the crankcase as nearly as possible.

The cylinders 12 are provided in the usual way with exhaust ports at 22communicating with manifolds 23 and mufller 24. Each cylinder has alsoan inlet or transfer port at 25 which at bottom dead center communicateswith the cylinder above and below the piston 26 therein. The pistonpreferably comprises a hollow body open at 2'? for intermittentcommunication with the exhaust port 22, and having an inclined that thecapacity of the space beneath the piston lower face at 28 for guidinggases to and from the compression space below the piston.

Controlling the admission of mixture to the inlet and transfer ports 25,is the rotary valve mechanism which comprises the particular subjectmatter of the present invention.

Each cylinder is provided with an integral forward extension at 30, ofwhich the cylindrical bore communicates with the cylinder through ports25. These bores are capped at their outer ends by closures 31, each ofwhich comprises a carburetor having a flaring air inlet mouth at 3 afloat chamber at 33, a jet at 34, and a throttle valve at 35.

The valves mounted in the bores of the respective cylinder extensions 30comprise sleeves 38, each of which is ported at 3'? and 38, the latterport being placed in direct communication with the air inlet valve 32 bymeans of a pipe 39 which is cast integrally with sleeve 36, and isformed to provide an axially disposed inlet portion at if), and aradially disposed discharge portion at 41. The discharge portion ll. ofpipe 39 is joined to the margin of the sleeve about the port 38 therein.

Each such sleeve is closely fitted to rotate within its respective bore,and each is provided with a shaft extension 43 upon which is mounted a'bevel gear 44. The two bevel gears 44 in the present constructionreceive motion from a bevel pinion 45, flexibly keyed to a jack shaft46. The jack shaft in turn is driven by a spur gear 47 from acomplementary spur gear 48 on the crank shaft. The hub of thislatter-gear extends into the upper crank shaft bearing. as shown in Fig.2. The jack shaft 46 may constitute a timer shaft provided with theinterrupter mechanism shown at 49. I

The flexible connection of the driving pinion 45 to the jack shaft ortimer shaft 46, is best shown in Fig. '7. Shaft 46 is provided with aslot at 50 in which the resiliently flexible spring key 51 is held by across pin 52. The free end of the resilient key 51 has arms 53 whichproject from the slot 50 into engagement with suitable --;-grooves inthe pinion 45, as shown in Fig. 2. The

result is a construction which permits pinion 45 a limited degree ofindependent movement with respect to the shaft 46 upon which it ismounted.

It will be understood that the two cylinders in this type of 7 enginefire simultaneously, and the energy developed in the expansion strokemust be used in the subsequent compression stroke. As a result, there isan appreciable cyclic change 1 in speed of crank shaft and fly wheel,and in .order to avoid transmitting this varying rate of rotationthrough the pinion 45 and driven gears 44 to the rotary valves, I may,if I so desire, employ the resilient pinion mounting illustrated.

In practice, the movement of the piston to the position in which itappears in Fig. 4 not only compresses the'combustible charge in theouter end of thecylinder, but draws a fresh charge through thecarburetor and the rotary valve'into the inner end of the cylinder nextto the crank case. As above noted, the charge for each givencylinder isdrawn directlyinto the base thereof. thus avoiding any necessity for thetransfer of gases across the crank case,'in-which the space is purposelyvery limited.

It will be noted from an inspection of Fig. 4

is at a minimum during the stroke which sucks the'fresh charge therein.The rotation of the valve sleeve 36 has brought pipe 39'through aposition of registry with the inlet of transfer port 25 through whichthe carbureted air or combustible mixture has been entering thecompression space. The remainder of sleeve 36 is completely cut off fromcommunication with this space. Practically the complete displacement ofthe piston, therefore, is effective to draw combustible mixture into theinner end of the cylinder' in accordance with the most approved twocyclepractice.

During the expansion stroke of the piston toward the position in whichit is shown in Fig. l, the valve sleeve 36 is caused to rotate to theposition shown in Fig. 1 whereby its pipe member 39 is wholly'cut offfrom communication with cylinder port 25. The cylinder port 25 has nowbeen placed in communication, through sleeve port 37, with the receiverin the interior of the valve sleeve 36 into which a large portion of thecombustible mixture has been forced by the descending piston 26. Thus,instead of holding un der high compression the large quantity of gasdrawn into the restricted sub-piston compression space, I have alreadycaused such gas to start on its movement toward the cylinder, and I amholding it under reduced compression in a space of very' much largercapacity than could have been provided in the cylinder and transfer portalone.

Ash. result of this constructionthe transfer of mixture to the cylinder,and the consequent scavenging of the exhaust gases from the cylinder,takes place more smoothly than has been possible in any two-cycle enginehaving a like efficiency of mixture intake. The power of the engine isgreatly increased by this means of controlled variation of the capacityof the sub-piston compression space and transfer port, whereby suchspace is at a minimum during the compression stroke, and is at a maximumduring the expansion stroke and transfer. 1 5

As an example of the timing of the rotary valve mechanism disclosed, Ishall refer to a particular engine embodying the invention in which thetransfer port 25 communicates almost continuously with one or the otherof ports3'7 and 120 38 of the valve. As soon as the piston 26 movesupwardly sufiiciently to cut off communication between the transfer portand the combustion chamber, port 38 moves into initial registry withtransfer port 25 to admit carbureted air to the sub-piston compressionspace. Port 38 continues open until the piston has started downwardly onits expansion stroke to a position representing approximately 25 degreesof crank rotation past top dead center. At this point port 38 closes andport 3'? moves into registration with transfer port 25, thereby allowingthe mixture compressed below the piston to pass into the receiver withinthe'valve sleeve 36 until the piston has completed its expansion strokeand moved upwardly to a point where the transfer of gas has ceased.

The organization disclosed will be found 'useful in many internalcombustion engine constructions using a means of compressing mixture inadvance of delivery to the combustion chamber. It will, however, befound particularly valuable in the type of two-cycle engine disclosed.

I claim:

1. An internal combustion engine comprising the combination with acylinder and crank case 145 assembly providing a sub-piston compressionspace including an open transfer passage controlled by said piston, of acrank shaft in said case, a receiver chamber provided with a portadapted for communication with said space, and 150 means operated bysaid crank shaft for intermittently opening and closing communicationbetween said chamber and space.

2. An internal combustion engine comprising the combination with apiston, a crank shaft, and a cylinder and crank case assembly providinga sub-piston compression space, of a chamber provided with a port forcommunication with said space, an air inlet conduit, and valve meansdriven by said crank shaft for timed control of alternatingcommunication of said space with said chamber and conduit.

3. An internal combustion engine comprising the combination with acylinder, a piston and an air compressor provided with a transfer portto the cylinder, of an air receiver and a single valve means controllingthe admission and discharge of air-from said compressor and adapted toplace said receiver in communication with said compressor during aportion of the period of discharge of air from the compressor, and tocut off said receiver from communication with said compressor during theperiod of admission of air to said compressor.

4. In an internal combustion engine, the combination with a piston and acylinder therefor, providing a sub-piston compression space and atransfer port affording communication controlled by said piston betweensaid space and the combustion chamber in said cylinder, and a rotarychamber operatively connected to be actuated from said piston andprovided with a port registerable with said transfer port during thecycle of piston movement during a period such as to limit compression insaid space.

5. In a two-cycle internal combustion engine, the combination with apiston, of a crank case, a cylinder providing a sub -piston compressionspace, valve means for admitting air thereto, a crank in said caseconnected with the piston,an auxiliary chamber provided with valve meanscontrolling communication between said chamber and said space, andconnections operatively arranged between said valve means and crankshaft for the operation of said last mentioned valve means to establishcommunication between said space and chamber during the piston movementcontracting said space, and to cut off such communication when said airadmitting valve means is operative.

6. A two-cycle internal combustion engine comprising the combinationwith a piston, of a cylinder and crank case assembly providing asub-piston compression space and a transfer port whereby delivery ofmixture from said space to the head of the cylinder may be effected atpredetermined periods in the cycle of piston operation, a crank shaft insaid crank case to which said piston is operatively connected, a storagechamber potentially communicating through said port with said space andthe head of the cylinder and provided with valve means controlling suchcommunication, and connections operatively arranged to actuate saidvalve means from said crank shaft in accordance with the cycle of pistonmovement, said chamber being cut off from communication with said spaceduring thelatter portion of that piston stroke by which said space isenlarged.

7. A multi-cylinder two-cycle engine including the combination with aplurality of pistons, a crank case, a plurality of cylinders for thepistons providing transfer ports respectively affording communicationbetween the heads of the cylinders and the crank case compression spacebeneath the pistons therein, and a crank shaft to which the severalpistons are respectively connected for simultaneous-inward and outwardmovement, said crank shaft, including means for filling substantiallyall crank case capacity not required for the piston connections, of aplurality of chambers potentially communicating with respectivecylinders and provided with valve means operatively connected foractuation by said crank shaft for controlling communication between saidchambersjand the compression space beneath the pistons of differentcylinders, whereby to vary the capacity of the respective spaces in thecycle of piston movement.

8. In an internal combustion engine, the combination with a piston, of acrank case and cylinder assembly for said piston providing a subpistoncompression space and a transfer port from said space to the head of thecylinder, a mixture inlet, an expansion chamber, and a valve operativelyconnected for operation from said piston and provided with meanscontrolling communication of said inlet and said chamber with saidspace, whereby said inlet and said chamber are alternately placed incommunication with said space during each cycle of piston movement.

9. In an internal combustion engine, the combination with a piston, of acrank case and cylinder assembly for said piston providing a sub-pistoncompression space and a transfer port from said space to the head of thecylinder, a mixture inlet, an expansion chamber, and a valve operativelyconnected for operation from said piston and provided with meanscontrolling communication of said inlet and said chamber with saidspace, whereby said inlet and said chamber are alternately placed incommunicationwith said space during each cycle of piston movement, saidchamber being excluded from communication with said space during theperiod of mixture admission responsive to outward piston movement, andsaid inlet being cut off from communication with said space during theperiod of mixture compression in and transfer from said space by inwardpiston movement.

10. Ina two-cycle engine, the combination with a crank case, a cylinderproviding an unobstructed transfer port from the crank case to thecylinder and a piston reciprocable in the cylinder and controlling saidport, of a mixture inlet, an expansion chamber, and means controlled inaccordance with piston movement for placing said inlet and chamberalternately in communication with said port.

11. In a two-cycle engine, the combination with a cylinder providing atransfer port and a piston reciprocable in the cylinder, of a mixtureinlet and an expansion chamber, and means controlled in accordance withpiston movement for placing said inlet and chamber alternately incommunication with said port, said means comprising a rotary valve, acrank shaft connected with the piston, and motion transmittingconnections between said shaft and valve.

l2.Ir 1 a two-cycle engine, the combination with a cylinder providing atransfer port and. a piston reciprocable in the cylinder to compressmixture alternately in the head thereof and in the sub-piston space andto control the transfer, of a rotary valve providing a mixture inletport and an expansion chamber alternately adapted to communicate withthe transfer port in the rotation of the valve, and means for rotatingthe valve in accordance with piston movement and in timed relation toadmit mixture to said space during piston induced depression therein,and to reduce compression of such mixture in said space during transferto the head by receiving a portion thereof into said chamber.

13. In a two-cycle engine, the combination with a cylinder providing atransfer port and a piston reciprocable in said cylinder to compressmixture alternately at one end or the other thereof, of means actuatedfrom the piston for admitting mixture to said transfer port duringcompression of mixture in the cylinder head, and means actuated from thepiston during its expansion stroke for interrupting the admission ofmixture and enlarging the capacity of the space accessible to themixture previously admitted.

14. In a two-cycle internal combustion engine, the combination with apiston and a crank case and cylinder therefor providing a sub-pistoncompression space and a transfer port, of a'rotatable chamber providedwith a port registerable with said transfer port during the contractionof said space by the expansion stroke of the piston, and meanscontrolled in accordance with the rotation of said chamber for admittinggas to said space during the enlargement thereof by the compressionstroke of the piston, said ports being out of registry.

15. A two-cycle engine comprising the combination with a piston and acylinder and crank case assembly providing a sub-piston compressionspace and a port leading thereto, of a crank shaft in said crank caseconnected with said piston, and an expansion chamber provided withrotary valve means controlling communication between it and said port,said means being connected with said crank shaft for operation inaccordance with piston movement to open communication to said chamberfrom said space during the contraction thereof by the expansion strokeof the piston.

16. A two-cycle engine comprising the combination with a piston and acylinder and crank case assembly providing a sub-piston compressionspace and a port leading thereto, of a crank shaft in said crank caseconnected with said piston, and an expansion chamber provided withrotary valve means controlling communication between it and said port,said means being connected with said crank shaft for operation inaccordance with piston movement to open communication to said chamberfrom said space during the contraction thereof by the expansion strokeof the piston, said rotary valve means including a gas inlet arranged tocommunicate with said port alternately with said chamber.

17. A two-cycle engine comprising the combination with a reciprocablepiston provided with a connecting rod and crank, and a cylinder andcrank case assembly for said piston, a crank having a sub-pistoncompression space and a transfer po t leading to the head of thecylinder, of a rotary valve structure including a peripherally portedreceiving chamber operatively connected to said crank and timed tocommunicate through said port with the transfer port substantiallyduringthe period of gas compression in said subpiston space and the period oftransfer of gas from said space to the combustion chamber, and a conduitcarried by said chamber and arranged to communicate with said transferport'for the admission of gas to the sub-piston space for theapproximate period during which gas may be drawn therein by pistonmovement.

18. Atwo-cycle engine comprising the com-- bination with a piston,connecting rod and crank, of a cylinder and crank case assemblyproviding a sub-piston compression space and a port opening thereto, achamber rotatably mounted adjacent said port and provided with acomplementary port adapted to communicate with said first mentioned portduring a predetermined period of chamber rotation, motion transmittingconnections between said chamber and crank shaft so timed with referenceto the movement of said piston as to place said chamber in communicationwith said space during a portion of the period of compression of gas insaid space, and a conduit leading through said chamber and communicatingwith said first mentioned port during a portion of the period for whichsaid chamber is out of communication therewith, said conduit beingadapted to admit air to said space during the said last mentionedperiod.

19. A two-cycle engine comprising the combination with a piston,connecting rod and crank, of a cylinder and crank case assemblyproviding a sub-piston compression space and a port opening thereto, achamber rotatably mounted adja cent said port and provided with acomplementary port adapted to communicate with said first mentioned portduring a predetermined period of chamber rotation, motion transmittingconnections between said chamber and crank shaft so timed with referenceto the movement of said piston as to place said chamber in communicationwith said space during a portion of the period of compression of gas insaid space, and a conduit leading through said chamber and communicatingwith said first mentioned port during a portion of the period for whichsaid chamher is out of communication therewith, said conduit having anopening disposed approximately upon the axis of said chamber and a pointof discharge approximately at the periphery thereof.

20. An internal combustion engine comprising the combination with apiston, connecting rod and crank shaft, and a cylinder and crank caseassembly providing a sub-piston compression space, of a valve chamberassociated with said cylinder and provided with a peripheral portcommunicating with said space and a substantially axial inlet, a valverotatable in said chamber and including a conduit from said axial inletto a peripheral point registerable with said port in rotation of saidvalve, and means for carbureting air adjacent said inlet.

21. In a .two-cycle engine, the combination with a crank case andopposed cylinders, a crank shaft in said case and pistons reciprocablein said cylinders and connected thereto, of valve chambers associatedwith the respective cylinders, rotary valves in said chambers havingperipheral ports and axial inlets at opposite ends of the respectivechambers, and separate means for carbureting air admitted to saidinlets.

22. In a two-cycle engine, the combination with a crank case and opposedcylinders, a crank shaft in said case and pistons reciprocable in saidcylinders and connected thereto, of valve chambers associated with therespective cylinders, rotary valves in said chambers having peripheralports and axial inlets at opposite ends of the respective chambers, andseparate means for carbureting air admitted to said inlets, therespective cylinders being provided with sub-piston compression spacesto which the carbureted air is admitted by the individual valves, andsaid crank shaft being formed to reduce the space for communicationbetween the compression spaces of the respective cylinders.

23. In a two-cycle engine, the combination I with a crank case andopposed cylinders, a crank ports and axial inlets at opposite ends ofthe respective chambers, and separate means for carbureting air admittedto said inlets, the respective cylinders being provided with sub-pistoncompression spaces to which the carbureted air is admitted by theindividual valves, and said crank shaft being formed to reduce the spacefor communication between the compression spaces of the respectivecylinders, each such valve having an auxiliary airreceiver communicatingwith said spaces alternatively with the air admission ports.

24. In a two-cycle, two-cylinder engine comprising a crank case andopposed cylinders, a crank shaft in said case and pistons in saidcylinders adapted for sub-piston compression, transfer passages aroundthe pistons, valve chambers ported for communication with said passages,rotary valves in the respective chambers controlling air admission tothe respective transfer passages, a common driving shaft to which saidvalves are geared and which is operatively connected to said crank shaftto receive motion therefrom, and means for carbureting air admittedthrough said valves to said passages.

25. In a two-cycle, two-cylinder engine comprising a crank case andopposed cylinders, a

crank shaft in said case and pistons in said cylinders adapted forsub-piston compression, transfer passages around the pistons, valvechambers ported for communication with said passages, rotary valves inthe respective chambers controlling air admission to the respectivetransfer passages, a common driving shaft to which said valves aregeared and which is operatively connected to said crank shaft to receivemotion therefrom, and means for carbureting air admitted through saidvalves to said passages, each of said valve chambers comprising anauxiliary receiver, and each of said valves having an auxiliary portregisterable with the transfer passage when the admission port is out ofregister therewith and adapted to admit transferred air to saidreceiver.

26. A two-cycle internal combustion engine comprising a crank case andopposed cylinders provided with transfer passages and associated valvechambers, carburetors at opposite ends of the respective chambers, andintergearedrotary valves in the chambers provided with inlets adjacentthe carburetors, and peripheral outlets adapted for registry with therespective passages in the course of valve rotation.

27. A two-cycle internal combustion engine comprising a crank case andopposed cylinders provided with transfer passages and associated valvechambers, carburetors at opposite ends of the respective chambers, andintergeared rotary valves in the chambers provided with inlets ad-.

jacent the carburetors, and peripheral outlets adapted for registry withthe respective passages in the course of valve rotation, and gasreceivers housed within. the respective valves and ported for registrywith the transfer passages when the said discharge ports are out ofregistry therewith.

28. A two-cycle internal combustion engine comprising a crank case andopposed cylinders provided with transfer passages and associated valvechambers, carburetors at opposite ends of the respective chambers, andintergeared rotary valves in the chambers provided with inlets adjacentthe carburetors and peripheral outlets ad'ap'ced for registry with therespective passages in the course of valve rotation, a crank shaft insaid case provided with pistons in said cylinders, and drivingconnections from said shaft to said valves including a flexible membersumciently yieldable to permit a substantially uniform valve speedirrespective of cyclic speed variation 'of said shaft.

29. An internalcombustion engine comprising the combination withacylinder and crank case assembly providing a transfer port, of a crankshaft in said crank case including means for filling unused capacitytherein, a piston reciprocable in the cylinder controlling communicationbetween said transfer port, a connecting rod between said piston andcrank shaft and the head portion of the cylinder, carbureting meansconnected with said cylinder at said transfer port, and a valveoperatively connected with said crank shaft for the timed admission ofcarbureted air to said transfer port and the cylinder space beneath saidpiston, said valve being arranged to close during the expansion strokeof said piston whereby the carbureted gas below the piston will becompressed in the transfer port immediately adjacent the head portion ofthe cylinder for instantaneous delivery thereto when said port isuncovered by the piston.

30. Aninternal combustion engine comprising the combination with acylinder and crank case assembly providing a transfer port, of a. crankshaft in said crank case including means for filling unused capacitytherein, a piston reciprocable in the cylinder controlling communicationbetween said transfer port, a connecting rod between said pis'ton andcrank shaft and the head portion of-the cylinder, carbureting meansconnected with said cylinder at said transfer port, and a valveoperatively connected with said crank shaft for the timed admission ofcarbureted air to said transfer port and the cylinder space beneath saidpiston, said valve being arranged to close during the expansion strokeof said piston whereby the carbureted gas below the piston will becompressed in the transfer. port immediately adjacent the head portionof the cylinder for instantaneous delivery thereto when said port isuncovered by the piston, together with a chamber connected with saidrotary valve for communication with said transfer port alternativelywith said valve, whereby the capacity'of said port is at a minimum whengases are being drawn therein on the compression stroke of the piston,and as a maximum upon communication of said chamber with said portduring the compression stroke of the piston.

31. An internal combustion engine comprising the combination with acylinder assembly providing a combustion chamber and a sub-pistoncompression space, a transfer port affording piston controlledcommunication between said space and chamber, and an exhaust portopening outwardly from said chamber, of a piston reciprocable in saidcylinder arranged to control said ports and having an internal cavityopening laterally below the face of the piston and positioned toregister with one of said ports when said port is closed by the piston.

32. An engine comprising the combination with a cylinder assemblyproviding a combustion chamber and a sub-piston compression space,transfer means affording piston controlled communication between saidchamber and space, and an exhaust port opening outwardly from saidchamber, of a piston reciprocable in said cylinder and arranged tocontrol said means and port, said piston having a bottom closure webdefining an interior cavity and having an opening through its side wallfrom said cavity arranged to register with said port when said port iscovered by the piston.

33. In an engine, the combination with a cylinder assembly provided witha combustion chamber and sub-piston compression space and havingtransfer and exhaust ports, of a piston reciprocable in said cylinderfor the control of said ports, said piston being closed ofi at itsbottom to limit the capacity of said space whereby to cause gasescompressed in said space to accumulate in said transfer port, and a partimmediately adjacent said port operatively connected with said pistonfor movement in synchronism therewith and including a valve for theadmission of fuel to said port, and a chamber arranged to communicatewith said port when said valve is out of communication therewith,whereby to increase the capacity of said port when mixture is compressedtherein and to reduce its capacity when mixture is being admittedthereto.

34. In an engine, the combination with a cylinder assembly provided witha combustion chamber and sub-piston compression space and havingtransfer and exhaust ports, of a piston reciprocable in said cylinderfor the control of said ports, said piston having an internal cavityopening laterally for registry with said exhaust port and bounded by alower closure wall inclined from the bottom of the piston on the exhaustport side thereof upwardly and across said piston to maintaincommunication between said transfer port and the sub-piston compressionspace.

FINN T. IRGENS.

